21545957 has 2 divisors, whose sum is σ = 21545958. Its totient is φ = 21545956.

The previous prime is 21545911. The next prime is 21545969. The reversal of 21545957 is 75954512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20349121 + 1196836 = 4511^2 + 1094^2 .

It is a cyclic number.

It is not a de Polignac number, because 21545957 - 2⁶ = 21545893 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21545957.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21545977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10772978 + 10772979.

It is an arithmetic number, because the mean of its divisors is an integer number (10772979).

Almost surely, 2^21545957 is an apocalyptic number.

It is an amenable number.

21545957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21545957 is an equidigital number, since it uses as much as digits as its factorization.

21545957 is an evil number, because the sum of its binary digits is even.

The product of its digits is 63000, while the sum is 38.

The square root of 21545957 is about 4641.7622731027. The cubic root of 21545957 is about 278.2628717937.

The spelling of 21545957 in words is "twenty-one million, five hundred forty-five thousand, nine hundred fifty-seven".